BBK PV420S, Руководство по обслуживанию

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– 143–
CXD3068Q
• 2N-track jump
When $4C ($4D for REV) is received from the CPU, a FWD (REV) 2N-track jump is performed in
accordance with Fig. 4-9. The track jump count N is set with register 7. Although N can be set to 2
16
tracks,
note that the setting is actually limited by the actuator. COUT is used for counting the number of jumps
when N is less than 16, and MIRR is used with N is 16 or more.
Although the 2N-track jump basically follows the same sequence as the 10-track jump, the one difference is
that after the tracking servo is turned on, the sled continues to move only for "D", set with register 6.
• Fine search
When $44 ($45 for REV) is received from the CPU, a FWD (REV) fine search (N-track jump) is performed
in accordance with Fig. 4-10. The differences from a 2N-track jump are that a higher precision is achieved
by controlling the traverse speed, and a longer distance jump is achieved by controlling the sled. The track
jump count is set with register 7. N can be set to 2
16
tracks. After kicking the actuator and sled, the traverse
speed is controlled based on the overflow G. Set kick D and F with register 6 and overflow G with register 5.
Also, sled speed control during traverse can be turned off by causing COMP to fall. Set the number of
tracks during which COMP falls with register B. After N tracks have been counted through COUT, the brake
is applied to the actuator and sled. (This is performed by turning on the tracking servo for the actuator, and
by kicking the sled in the opposite direction during the time for kick D set with register 6.) Then, the tracking
and sled servos are turned on.
Set overflow G to the speed required to slow up just before the track jump terminates. (The speed should
be such that it will come on-track when the tracking servo turns on at the termination of the track jump.) For
example, set the target track count N –
α
for the traverse monitor counter which is set with register B, and
COMP will be monitored. When the falling edge of this COMP is detected, overflow G can be reset.
• M-track move
When $4E ($4F for REV) is received from the CPU, a FWD (REV) M-track move is performed in
accordance with Fig. 4-11. M can be set to 2
16
tracks. Like the 2N-track jump, COUT is used for counting
the number of moves when M is less than 16, and MIRR is used when M is 16 or more. The M-track move
is executed by moving only the sled, and is therefore suited for moving across several thousand to several
ten-thousand tracks. In addition, the track and sled servos are turned off after M tracks have been counted
through COUT or MIRR unlike for the other jumps. Transfer $25 from the microcomputer after the actuator
has stabilized.